The present invention relates to a method for azide displacement of .alpha.-triflates of 1,5-lactones.
Sugar lactones have been used heretofore as intermediates for the synthesis of highly functionalized nitrogen heterocycles. See Fleet et al., Tetrahedron, 45, 319-326 (1989) and references cited therein. See also U.S. Pat. No. 4,861,892 concerning the synthesis of deoxymannojirimycin from gulonolactone. The readily available acetonide of glucuronolactone, in which only the C-5 hydroxyl group .alpha.- to the carbonyl group is unprotected, has been used in the synthesis of a number of D- and L-amino acids. See Bashyal et al., Tetrahedron, 43, 415-422 (1987) and Bashyal et al., Ibid. 43, 423-430 (1987).
Suitably protected heptonolactones with seven adjacent functional groups and five adjacent chiral centres can provide powerful intermediates for the synthesis of complex and highly functionalized targets. The epimeric lactones (1) and (3) disclosed herein can be obtained as a mixture in which the lactone (1) predominates from the treatment of diacetone mannose (7) with sodium cyanide. The stereoselectivity in this reaction is in marked contrast to that observed in the reaction of cyanide with mannose. See Montgomery and Hudson, J. Am. Chem. Soc. 64, 247 (1942); Karabinos et al., Ibid. 75, 4320 (1953). ##STR1##